This invention relates to a ventilation system for a multi-storey building, which system comprises
an apparatus mounted on the roof of the building with fans for generating an inlet air flow PA1 a distributing channel for supplying the inlet air flow to various intermediate levels of the building. PA1 that a service shaft of the building or a similar space extending vertically through the building and opening to the intermediate levels serves as an inlet air flow channel, forming a flow path for the inlet air flow directed from the fans downwards, PA1 that the service shaft has deflecting means for passing a part of the air flow to each intermediate level of the building.
and
In high buildings, in which indoor air is warmer than outdoor air, a pressure difference arises between the upper and lower part of the building. Since buildings are not airtight, air leaks through the constructions from the upper part of the building outwards and from the lower part inwards. Inside the building the air flows from below upwards.
Because of leaks, the lower part of the building is cold and draught often appears therein. In the upper part it is easily hot and if the humidity of the indoor air is clearly higher than the humidity of the outdoor air, leaking air may condense to water in the constructions. Impurities are spread by the internal air flows of the building.
These drawbacks can be prevented by constructing the intermediate levels as airtight as possible in the building. In residential and office buildings, for instance, the building has thus been successfully divided into parts independent of each other, within which the effects of the pressure difference can be eliminated by conventional air-conditioning techniques thanks to the slightness of the pressure difference.
In industrial buildings again, in which there are many big passages for production equipment, manholes holes and service shafts etc. through the levels, it would be extremely expensive and difficult, if not directly impossible, to build airtight levels.
If there are no intermediate levels in the building, temperature differences between the upper and lower part of the building can be equalized by means of strong air jets, which extend from the vicinity of the roof nearly to the plane of the floor, bring along air from the upper part of the building and mix it effectively. Such a system is known from Finnish Patent no. 56 714.
Such a system cannot be used in multi-storey buildings, even though the intermediate levels were air permeable, such as plane grates, because areas with strong air jets are not suited for working places.
If there are only a few intermediate levels, pressure and temperature differences have been equalized by means of axial-flow fans mounted on the levels, which fans blow air from an upper level downwards. Still, they take up valuable floor space, cause noise problems, consume electric power and are relatively ineffective with respect to balancing the temperature, because the air from the fan is in a strong rotating motion. The air does not flow as a jet to a lower level, but spreads along the ceiling of the lower level, whereby no mixing to balance temperatures occurs.
So, temperature and pressure differences in high multi-storey buildings generally tend to be reduced in such a way that a maximum part of the ventilation air is passed through channels to the lower part of the building and only a minimum air flow necessary for the air quality to the upper part. Pressure differences can thus be slightly equalized, which has some effect on leaks and temperature differences, but the air flow required for the ventilation generally is quite insufficient for an effective pressure balancing. The channels take up space in the building, to build them causes costs and to locate them in the building is difficult. An effective air distribution by means of conventional air distributing devices to often wide levels seldom succeeds without distributing channels, which additionally increases the costs. A problem of its own is caused by the regulation. A pressure and temperature difference in a building depends on the temperature difference between the indoor and outdoor air, according to which it should be possible to regulate the ratio of the inlet air flows of the upper and lower part of the building. This is not possible in practice because of the high costs due to the great amount of both air distributing and regulating devices. The result of the above is that e.g. the lower part of the building is subjected to underpressure in winter and to overpressure in summer. The pressure ratios are opposite in the upper part and the air quality is often bad.